A known instrument panel reinforcement supporting interior parts constituting an instrument panel of a vehicle is disclosed in JP2011-189806A (hereinafter referred to as Patent reference 1). Generally, the weight of a part of the interior parts constituting the instrument panel of the vehicle disposed at a front passenger's seat side (a passenger's seat side next to a driver's seat side) is lighter than that of a part disposed at the driver's seat side. Accordingly, the strength of the part of the instrument panel reinforcement disposed at the front passenger's seat side does not have to be as strong as the part disposed at the driver's seat side. Here, in Patent reference 1, the part of the instrument panel reinforcement disposed at the front passenger's seat side is formed thinner than the part disposed at the driver's seat side.
The weights of the plural interior parts mounted on the part of the instrument panel reinforcement disposed at the front passenger's seat side differ from one another. Thus, it is favorable that a part where relatively heavy interior parts are mounted, or a part in the vicinity of the part where the relatively heavy interior parts are mounted, includes the strength that is set relatively high. The part of the instrument panel reinforcement disclosed in Patent reference 1 is formed by the bending of a plate member into a cylindrical shape. Accordingly, it is difficult to set the part or the part in the vicinity of the part where the relatively heavy interior parts are mounted to include the strength higher than other parts. That is, an outer diameter and a plate thickness of the part disposed at the driver's seat side are unchanged in a longitudinal direction, and the strength of the part disposed at the front passenger's seat side is unchanged in the longitudinal direction. In addition, for example, it is difficult to set the strength of a local part disposed at a front of a passenger high so as to protect the passenger when the vehicle collides. Accordingly, in the instrument panel reinforcement disclosed in Patent reference 1, the outer diameter and the plate thickness of the whole parts disposed at the front passenger's seat side are set focusing on that the strength is required to be set relatively high. That is, the outer diameter and the plate thickness of the part are set unnecessarily high even for the part strength of which does not have to be set high. Accordingly, the weight of the part disposed at the front passenger's seat side unnecessarily increases.
A need thus exists for an instrument panel reinforcement which is not susceptible to the drawback mentioned above.